OBJECTIVE: The major goals of this projects were to establish baseline data in the laboratory on the social and hormonal mechanisms by which induction and release of reproductive inhibition can occur in daughter common marmosets; to provide a basic understanding of fecal cortisol responses to female ovarian function and intergroup movements in daughters, and to use these data to interpret the first endocrine data to be collected under field conditions for the common marmoset. RESULTS Reproductive and adrenal steroids were easily monitored through fecal steroid analysis and demonstrated responses to social environment. Diurnal variation was found in both cortisol and progesterone excretion into the feces of the female common marmoset but not for estradiol which appears to have a delayed excretion rate. Half of the daughters began ovarian cycling while remaining with the natal family and all daughters showed an increase in cortisol levels when paired with a male. Reintroduction back into the family did not suppress ovarian function but did re-elevate cortisol levels. There was no difference in cortisol levels between cycling mothers and their cycling or noncycling daughters but noncycling mothers had lower levels of cortisol. Only one mother became aggressive when the daughter was reintroduced back into the family after a two month pairing with a male. These data support the hypothesis that female marmosets may be allowed to re-enter their groups in the wild and that social change is associated with increased adrenal function. FUTURE DIRECTIONS Fecal samples have been collected from over five different groups of wild marmosets at Nisia Floresta in Brazil. These samples are currently being analyzed for steroids. KEY WORDS fecal steroids, adrenal response, social stress, ovarian cycling, soicoendocrinology